1. Field of the Invention
The present invention relates to a latch device for a runner member used in a passive type seat belt system. More particularly the present invention relates to a latch device which automatically latches the runner when it comes to its passenger restraining position in association with closing of a door or the like and automatically unlatches the runner when it is about to move from the passenger restraining position to its passenger releasing position in association with opening of the door or the like. By the term "passenger" as used herein is meant any person occupying a seat in a vehicle including a driver.
2. Description of the Prior Art
For the passive type seat belt system there have been proposed and used many latch devices designed to latch the runner in the passenger restraining position. However, many of the known devices are unsatisfactory as regards security and reliability. In an emergency such as a collision, the latch device is subjected to a strong impact force or deformation tending to cause a violent unlatching. The latch device should be safe against such accidental unlatching. Also, when load is applied to the webbing fastened to the runner, the webbing may run idly until it is completely latched, which can also be dangerous. The latch device should be designed to minimize such danger caused by idle running of webbing. It is always desired that the latch device be high in operational reliability and simple in structure. In these respects, many of the known latch devices have some problems.